#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	int i = 0;
	double sum = 0;
	int flg = 1;
	for (i = 1; i <= 100; i++)
	{
		sum += 1.0 / i*flg;
		flg = -flg;
	}
	printf("%lf", sum);
	return 0;

}